Ten years after Steve Jobs held up the original iPhone to a gushing San Francisco crowd, Apple Inc. is planning its most extensive iPhone lineup to date.

Apple is preparing three iPhones for launch as soon as this fall, including upgraded versions of the current two iPhone models and a new top-of-the-line handset with an overhauled look, according to people familiar with the matter. For the redesigned phone, Apple is testing a new type of screen, curved glass and stainless steel materials, and more advanced cameras, the people said. Those anxiously awaiting the redesigned iPhone, however, may have to wait because supply constraints could mean the device isn't readily available until one or two months after the typical fall introduction.

The iPhone is Apple’s most important product, representing about two-thirds of sales. It also leads customers to buy other Apple devices like the iPad and Apple Watch, and serves as a home for lucrative services like the App Store. This year's new iPhone lineup comes at a critical time. Last year, Apple broke its typical upgrade cycle by retaining the same iPhone shape for a third year in a row and endured a rare sales slide. Samsung Electronics Co.'s new S8 lineup has also been thus far well received after last year's Note 7 battery debacle.

For the premium model, Apple is testing a screen that covers almost the entire front of the device, according to people familiar with the matter. That results in a display slightly larger than that of the iPhone 7 Plus but an overall size closer to the iPhone 7, the people said. Apple is also aiming to reduce the overall size of the handset by integrating the home button into the screen itself via software in a similar manner to Samsung's S8, the people said.